Atrial fibrillation (AF) is a form of abnormal heart rhythm (often referred to as cardiac arrhythmia), and involves the muscles of the upper two chambers of the heart (the atria) quivering rather than contracting in a more coordinated manner. As many as 6 million people in the United States suffer from AF, and may be candidates for atrial appendage intervention. AF is the second leading cause of stroke in the United States and may account for nearly one-third of strokes in the elderly. As our population continues to age, this problem may become even more prevalent.
In greater than 90% of cases where a blood clot (thrombus) is found in the AF patient, the clot develops in the left atrial appendage (LAA) of the heart. The LAA is a pouch of heart muscle attached to the left atrium. Removal of the LAA may result in a reduction of the incidence of stroke in AF patients, and there is growing interest in both surgical and endovascular methods to remove the LAA.
The literature on the correlation between the LAA, thrombus formation, and stroke is largely based on a number of individual cases. While the pathophysiology of thrombus formation in the LAA remains poorly understood, these studies suggest that there exists an increased risk for thrombus formation when closure of the LAA is unsuccessful. Excision appears superior to other methods such as stapler or suture exclusion in patients undergoing cardiac surgery, but is not always practical. In an internal review of 49 patients, failure was found in 40% of cases after surgical LAA elimination.
New devices to percutaneously occlude the LAA have been developed for stroke prophylaxis and seem promising. These new devices include the use of a clip to clamp the LAA shut, the use of a snare to wall off the LAA, the use of an umbrella device to expand the LAA, the use of a device which may close the LAA but not obliterate it, and the use of a device which may fill the LAA without closing it. Data on the safety and efficacy of these devices must be considered over time. These new devices are early in clinical trials and have several limitations. For instance, use of the clip to clamp the LAA shut may not get down to the base of the LAA, may leave a residual stump or leak, may result in a clot forming, and may require open surgery. Use of the snare may leave a residual stump or leak, may be less controlled, and may not be possible if adhesions are located around the heart. Use of the umbrella device may require the patient to be on blood thinners since it is made out of a foreign material and does not occlude and obliterate the LAA simultaneously. Use of a device which may close the LAA without obliterating it, and use of a device which may obliterate the LAA without closing it are both incomplete solutions which may experience leakage, which may require blood thinners due to the use of synthetic materials, or which may experience other types of issues.
There is a need for an occluder system and method for occluding or obliterating the LAA while overcoming one or more issues of the existing systems and methods.